首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 273 毫秒
1.
Agrotis ypsilon andSpodoptera littoralis can be successfully controlled on various field crops usingBacillus thuringiensis (Dipel 2X) baits and sprays. Baits based on the pathogen at 200–250 g/Feddan, scored the best efficacy againstA. ypsilon in clover fields followed by potato, tomato, and cotton cultivations. Addition of some chemical additives (inorganic salts) toB. thuringiensis bait formulations greatly enhanced its potency. This was associated with an obvious increase in the yield of clover, potato and tomato crops; calcium oxide showed to be highly afficient in this respect. Sprays of Dipel 2X were also found as affective as lannate in controllingS. littoralis on clover cultivations.
Zusammenfassung Die Untersuchungen ergaben, daßAgrotis ypsilon undSpodoptera littoralis an verschiedenen Feldfrüchten erfolgreich mitBacillus thuringiensis (Dipel 2X) als Köder oder Sprühmittel bekämpft werden können. Die Köder auf der Grundlage von 200–250 gBacillus/Feddan erzielten die besten Ergebnisse gegenA. ypsilon auf Kleefeldern, gefolgt von Kartoffel, Tomate und Baumwolle. Die Beimengung von chemischen Zusatzmitteln (anorganische Salze) zu denBacillus-Ködern erhöhte die Wirksamkeit beträchtlich. Daraus resultierte eine auffallende Steigerung der Klee-, Kartoffel- und Tomatenernte. Dabei war Kaliumoxid das wirksamste Zusatzmittel. Das Sprühen mit Dipel 2X erwies sich in Kleefeldern als ebenso wirksam wie die Anwendung des chemischen Pestizids Lannate.

With 4 tables  相似文献   

2.
Field tests were conducted to determine the effectiveness of wheat-brain baits based onBacillus thuringiensis var.kurstaki HD-1 (dipel 2x) compared to the organophosphorous insecticide Hostathion against the greasy cutwormAgrotis ypsilon infestations on horse bean (Vicia fabae) cultivations. Significant larval reductions were observed in all treated plots after one application with a significant increase in the yield (1.45–1.60 folds) compared to the control plots. The yield was not obviously affected by varying the dose of dipel in the bait between 150–250 g/feddan. The addition of the adjuvant potassium carbonate to the dipel bait caused a significant larval reduction, 10 days after application and showed to be as efficient as baits based on Hostathion.  相似文献   

3.
Field applications usingBacillus thuringiensis (Dipel 2 X) againstSpodoptera exigua infesting corn and sunflower cultivations were carried out in two different localities in Egypt. The percentage of infested corn plants decreased to 2.5%, seven days after treatment with Dipel 2x, (250 g/fed) and the yield was significantly increased compared with untreated plots. The carbamate insecticide (Lannate) at 300 g/fed caused complete kill to the larvae and the highest yield was obtained. Application of Lannate, Dipel (250 g) or a combination of both (150 g/each/fed) caused a high reduction of the larvae existing in sunflower after seven days from application, while Dipel at 200 g/fed gave a lower effect. Ten days after application, the number of larvae and infested plants increased significantly in plots treated with Lannate alone, while plots treated with either Dipel (250 g) or Dipel combined with Lannate (150 g/each) still maintained a lower infestation. The estimated yield showed the highest increase in plots treated with Lannate followed by Dipel (250 g) and then a combination of both.  相似文献   

4.
The potential activity of different varieties ofBacillus thuringiensis was evaluated against the second instar larvae of the two lepidopterous corn borersChilo agamemnon andOstrinia nubilalis. Data on the LC50, slopes, 95% confidence limits and potencies of the tested varieties were determined. WithO. nubilalis, Dipel 2X (Bacillus thuringiensis. var.kurstaki HD-1) was the most potent and the LC50 was 2.68 μg/g diet. The LC50 for other varieties ranged between 3.12 and 31.95 μg/g. In the case ofC. agamemnon, the lowest LC50 was also determined with Dipel 2X being 3.68 μg/g diet; this ranged between 6.2–15.11 μg/g for other tested varieties.  相似文献   

5.
The efficacy of the commercial product Dipel 2X (Bacillus thuringiensis var.kurstaki), was assessed as a biological control means of the cotton leaf wormSpodoptera littoralis attacking clover cultivations (Trifolium alexandrinum) in Egypt. Field experiments using the biological agent were carried out in two localities as compared with the conventional chemical insecticide lannate. The percentage of reduction in the larval population increased at higher doses ofB. t. and the infestation levels reached very low levels, almost similar to those obtained after using lannate. The yield of the first cut of clover was estimated. The data obtained indicate that the yield significantly increased after treatment with eitherB. t. or lannate. In Menoufia, the yield was significantly higher after two successive spray applications withB. t. at 750 g/f compared to that obtained withB. t. when used at 500 g/f. In Giza Governorate, the yield was slightly higher after a single treatment withB. t. at 500 g/f as compared with lannate.  相似文献   

6.
An area of 50 feddans cultivated with soybeans was treated withBacillus thuringiensis (B.t.) baits againstAgrotis ypsilon and 60 feddans were sprayed withB.t. spray againstSpodoptera littoralis. WhenB.t. baits were used, the percentage of kill ofA. ypsilon reached 96.1–96.4% compared to 97.4–98% kill on using hostathion baits. WhenB.t. was sprayed againstS. littoralis, a percentage of larval kill 88.3% was obtained. This increased to 97.3% after the second application. On the other hand, the precentage of kill reached 96.8% when lannate was sprayed once. The average yield was 1.54 tons/fed. whenB.t. was sprayed twice againstS. littoralis and 1.42 tons/fed. when sprayed once. Areas, treated with lannate gave 1.44 tons/fed., while in the untreated area the yield was comparatively low being 0.83 tons/fed.Mith 4 tables  相似文献   

7.
Field experiments have been carried out to evaluate the potency of the biological control agentBacillus thuringiensis (Dipel), the pyrethroid Fenvalerate and their combinations for the control of the lesser cotton leafwormSpodoptera exigua on soybeans in Qualubia governorate. Molasses was combined with all treatments to enhance their effectiveness. One spray application with either Dipel or Fenvalerate showed an obvious reduction in larval counts ofS. exigua, associated with a significant increase in the crop yield but in varying degrees, in correlation with the tested dose. Treatments with combinations of both biological and chemical insecticides at the lowest tested doses (62 g ofB. t. +50 ml of Fenvalerate/feddan) showed to be highly potential, and caused 2.8 fold increase in the crop yield. It may be recommended that a combination of both preparations may be used for the control ofS. exigua.  相似文献   

8.
Due to the fact that the persistence ofBacillus thuringiensis (B.t.) is very short in the field as affected by exposure to ultraviolet radiation, some biochemical approaches have been adopted in an attempt to increase potentiation of the pathogen against the two lepidopterous corn borers,Chilo agamemnon andOstrinia nubilalis. These approaches were based on the incorporation of some selected non-toxic chemical compounds with different modes of action with the endotoxin ofB.t. fed to the larvae and thus resulting in its potentiation. Among the compounds tested, some representatives of inorganic salts, organic acids, protein and lipid solubilizing agents, amino acids and amides showed an obvious potentiation to the endotoxin activity against the target insects. Inorganic salts, such as, calcium oxide, calcium carbonate, zinc sulphate and potassium carbonate at 0.1% potentiated the activity of the product Dipel 2X (B.t. var.kurstaki) against the two tested species in varying degrees. With regard to protein solubilzing agents, urea, sodium thioglycollate and EDTA enhanced the potency ofB.t. againstO. nubilalis with a fold increase of 1.4–2.3. The lipid emulsifying agent Tween 80 (0.5%), caused 1.3 fold increase in the potency ofB.t. With respect toC. agamemnon, sodium thioglycollate and EDTA (0.1%) were effective in potentiating the activity ofB.t. with fold increase of 3.1 and 1.2, respectively, while urea caused a decrease in the potency ofB.t as compared with the control. The lipid emulsifying agent Tween 80 (0.5%) caused 1.3 fold increase in the potency ofB.t. The potentiating effect of aromatic compounds is not obvious with respect to the tested insect species. With amino acids and amides, it appears that some of the tested compounds enhanced the potency ofB.t. against the tested insect species but in varying degrees. The mode of action of the tested compounds has been discussed in the light of the results obtained.  相似文献   

9.
Transgenic Bt-cotton now dominates the cotton-growing belt in northwestern China where there are few natural plant refuges to act as sources of moths susceptible to Bt toxin. As an initial step towards developing an insect resistance management (IRM) plan for the pest moth, Helicoverpa armigera, on Bt-cotton in this part of China, we assessed the potential of six crops grown in two configurations to act as refuge hosts for susceptible moth production in both broad-acre and small-holder farms. Egg and larval abundance indicated that H. armigera had a preference for chickpea, pigeon pea, and corn, over cotton, sorghum, and benne (sesame). There were no significant differences in egg or larval abundance between plot and strip configurations of these crop hosts. We found that sorghum was not attractive to H. armigera, contrary to the findings in other cotton production areas. Moreover, chickpea, pigeon pea, and corn were determined to be potential refuge hosts based on egg and larval abundance over the growing season. From the adult moth population dynamics in broad-acre and small-holder farms, the efficiency of alternative refuge crops, and local agricultural practices, we recommend that spring corn be grown as a strip crop as part of an IRM strategy to improve the probability of Bt-susceptible moth production and mating with resistant moths in broad-acre farms. In small-holder farms where current agricultural practices are entrenched, wheat and summer corn should be evaluated as refuge crops in the future.  相似文献   

10.
Tests with different rodenticides against the Iberian Vole (Microtus lusitanicus) and the Mediterranean Vole (M. duodecimcostatus) were carried out in highly infested orchards in Portugal. Best results were obtained with baits containing 0.005% Bromadiolon. Broken carob was a suitable bait material. Apple slices and granulats of lab chow were also accepted, but were destructed very fast by fungi. Cultivation techniques had a great influence on the results. The density of Iberian Voles could be diminished drastically with a combined method of removing the ground cover and subsequent application of poisoned baits. Blowing anticoagulant dusts directly into the galleries of the voles was not very successful until now.  相似文献   

11.
The Common Vole (Microtus agrestis) and the Redbacked Vole (Clethrionomys glareolus) can cause severe damages in forest plantations. Different application techniques of rodenticides to control these harmful rodents were tested by several institutions of plant protection in the Federal Republic of Germany. The following registered baits were used: A bluestained pectin-wax pellet containing 0.0075% Chlorphacinon (Lepit®-Forstpellet), small flour-plates (Arrex®-M-Köder klein) and sunflower kernels coated with plastique-foil (Arrex®-E-Köder) both incorporated with 2% resp. 3.75% zinc-phosphide. In 1985 disperse spraying versus concentrated offering of the baits in 12 earthenware pipes/ha was tested. The density of mice and voles could be reduced nearly to the same level with both methods. However, the amount of baits needed was much less when bait stations were used. In 1986 a new and save type of bait station (Theyson-Köder-station) was tested, from which non-target animals cannot get baits. The acceptance of the bait station could be improved by aromatic compounds from apples. According to the obtained first results forest plantations can be protected during the whole wintertime against vole-damages by means of bait stations.  相似文献   

12.
Outbreaks of the Nun Moth (Lymantria monacha L.) are known from 11 Danish localities. Three started in 1971–72, and 5 in the period 1979–81. Several insecticides were used controlling the outbreaks. Very efficient was endosulfan—and immediate—but it inflicted some bird losses. Very efficient was also difluron, but its slow action could not be accepted at the higher population levels. Less efficient was trichlorfon andBacillus thuringiensis (Dipel). The latter failed completely in one year presumably due to a temperature fall. Prognosis and especially the need for a two-year prognosis are discussed.  相似文献   

13.
The relation between the pathogenBacillus thuringiensis and the predatorOrius albidepennis (Hem.: Anthocoridae) associated with the greasy cutwormAgrotis ypsilon (Lep.) has been investigated. The biology of the predator showed to be affected in terms of nymphal duration, rate of food consumption and egg production when the predator larvae were fed on treated eggs or neonate larvae of the host (A. ypsilon). The effect of B-exotoxin (thuringiensin) on the predator has been also demonstrated.  相似文献   

14.
The effect of different host plants including cabbage, cauliflower, mustard, radish, and broccoli on biological parameters of Pieris brassicae (L.) was studied in the laboratory at 28°C, 65 ± 5% RH and 12L:12D photoperiod. Duration of each life stage, longevity, the intrinsic rate of natural increase (r m), net reproductive rate (R 0), mean generation time (T), doubling time (DT), and finite rate of increase (λ) of the cabbage white butterfly on the different cole crops were estimated. Differences in fertility life table parameters of the P. brassicae among host plants were analyzed using pseudo-values, which were produced by Jackknife re-sampling. The results indicating that cabbage might be the most suitable food for P. brassicae due to the shorter development time (16 days), longer adult longevity (12 and 9 days for female and male, respectively), higher fecundity (281 eggs/female), higher intrinsic rate of natural increase (0.1156 females/female/day), lower doubling time (6.00), lower larval mortality (70.33%), and higher yield of adult (30%). Therefore, it can be concluded from the present study that P. brassicae prefers cabbage for fast and healthy development with low larval mortality and highest number of adult yield than other cole crops.  相似文献   

15.
The Egyptian cotton leafworm,Spodoptera littoralis Boisd., is the main important pest of alfalfa in Israel. Population levels of other pests usually do not reach the economic threshold. Nine chemical insecticide applications (7 spray applications and 2 granular fluorosilicate baits) were required to controlS. littoralis during the season of 1984 (in which infestation level was high) whereas only 5 applications of aBacillus thuringiensis var.entomocidus (Bte) preparation (3 sprays and 2 baits) produced the same effect. During 1983 and 1985 pest populations were moderate and only 6 chemical pesticide applications were required. A bait ofBte on wheat bran, Coax®, developed in the present study was effective in the control of large larvae (instars 4–6). Hay yields of fields treated withBte were similar to the yields of a conventionally treated field. The best control of large larvae was obtained by applying the bait preparation under the wind row during the alfalfa cutting.  相似文献   

16.
Historical logging, fire suppression, and an invasive pathogen, Cronartium ribicola, the cause of white pine blister rust (WPBR), are assumed to have dramatically affected sugar pine (Pinus lambertiana) populations in the Lake Tahoe Basin. We examined population- and genetic-level consequences of these disturbances within 10 sugar pine populations by assessing current population structure and trends for 1129 individuals, genetic diversity for 250 individuals, and frequency of WPBR-resistance for 102 families. Logging had occurred in 9 of 10 sites and fire suppression was evident in all stands. High density of white fir (Abies concolor) is often an indicator of fire suppression and we found a negative relationship between sugar pine survivorship and white fir basal area (r2 = 0.31). C. ribicola was present in 90% of stands (incidence range: 0-48%) and we found a significant relationship between mean host survivorship and disease incidence (r2 = 0.46). We estimated population growth rates (λ) from size-based transition matrices. For six of 10 sugar pine populations λ was ?1.0, indicating that these populations appear to be stable; for four populations, λ was <1.0, indicating populations that may be in decline. A population specific drift parameter, ci, which is a measure of genetic differentiation in allele frequencies relative to an ancestral population, ranged from 0.009 to 0.048. Higher values of ci indicate greater genetic drift, possibly due to a bottleneck caused by historical logging, other agents of mortality or much older events affecting population sizes. Effects of drift are known to be greater in small populations and we found a negative relationship between sugar pine density and ci (r2 = 0.36). Allele frequency of the Cr1 gene, responsible for WPBR-resistance in sugar pine, averaged 0.068 for all populations sampled; no WPBR infection was found in one population in which the Cr1 frequency was 0.112. Historical disturbances and their interactions have likely influenced the population biology of sugar pine in the Tahoe Basin; for some populations this has meant reduced population size, higher genetic drift, and poor survival of small- and intermediate-sized individuals. Possible management strategies include restoring population numbers, deploying WPBR-resistance, treating stands to promote natural sugar pine regeneration, and enhancing genetic diversity.  相似文献   

17.
Using nine microsatellite loci, we studied the effects of selective logging on genetic diversity, mating system and pollen dispersal in a population of the tree species Hymenaea courbaril, located in a 546 ha plot in the Tapajós National Forest, Pará State, Brazil. We analyzed 250 offspring (nursery reared seedlings) collected after a logging episode from 14 open-pollinated seed trees. These were compared to 367 seedlings from 20 open-pollinated seed trees previously collected from the pre-logging primary forest. The genetic diversity was significantly lower in the post-logging seed cohort. In contrast to the pre-logging population, significant levels of selfing were detected in the post-logging population (tm = 0.962, P < 0.05). However, correlated matings were reduced and the effective number of pollen donors almost doubled after harvesting (3.8 against 7.2). Logging also reduced pollen immigration into the plot (from 55% to 38%) and we found no significant correlation between the size of the pollen donors and the number of seeds fathered. Inside the plot, pollen dispersal distance was shorter before logging than after (827 and 952 m, respectively) and the reproductive pollination neighbor area (Aep) was larger (average of 178 ha). The individual and average variance effective population size within families (ranged from 1.80 to 3.21, average of 2.47) was lower than expected in panmictic populations (Ne = 4). The results indicate that while logging greatly reduced the levels of genetic diversity after logging, it also increased genetic recombination within the population and constrained crossing among related individuals. The results show that low-density tropical tree species such as H. courbaril, when harvested in moderate levels may be resilient to a reduction in the reproductive population and may maintain similar levels of outcrossing and pollen dispersal after logging.  相似文献   

18.
The success of agroforestry in semi-arid areas depends on efficient use of available water and effective strategies to limit tree/crop competition and maximise productivity. On hillsides, planting improved tree fallows on the degraded upper section of bench terraces is a recommended practice to improve soil fertility while cropping continues on the lower terrace to maintain food production. This study examined the influence of tree fallows on soil water content (θ w ) and evaporation (E s ). Alnus acuminata Kunth (alnus), Calliandra calothyrsus Meissner (calliandra), Sesbania sesban L. (sesbania), a mixture of all three species, or sole crops (beans (Phaseolus vulgaris L.) or maize (Zea mays L.)) were grown on the upper terrace. The same sole crops were grown on the lower terrace. Four management regimes (unpruned, root, shoot and root + shoot pruned) were applied to the tree rows adjacent to the cropping area. Neutron probe and microlysimeter approaches were used to determine θ w and E s when the trees were c. 3.5 years old. Sesbania and alnus increased θ w by 9–18 % in the cropping area on the lower terrace but calliandra reduced θ w by 3–15 %. After heavy rain, E s comprised 29–38 % of precipitation in the tree-based treatments and 53 % under sole crops. Absolute values declined as rainfall decreased, but E s as a proportion of rainfall increased to 39–45 % in the tree-based treatments and 62 % for sole crops. Root + shoot pruning of alnus and the tree mixture increased θ w in the cropping area but had no significant effect in the other tree-based treatments. The results suggest that sesbania and alnus can be planted on smallholdings without compromising water supply to adjacent crops, whereas calliandra decreased water availability despite reducing E s . These results provide a mechanistic understanding of reported effects on crop yield in the same site.  相似文献   

19.
Investigations conducted in the laboratory for comparing the efficacy of phosphine with that of mixtures of the gas plus carbon dioxide against diapause larvae ofTrogoderma granarium showed that addition of varying concentrations of CO2 (20, 50, 75 and 100%) to fixed PH3-concentrations had a negative influence on phosphine efficacy against diapause larvae of Khapra Beetle at 30°C for short exposure periods of 18 and 24 hours. On the other hand, it was found that for longer exposure periods of 48 and 72 hours, the addition of CO2 to phosphine induced significantly higher larval mortality than that by PH3 alone, whereby an additive effect was proved for mixtures contained PH3+75% and 100% CO2. The addition of 20% and 50% CO2 to PH3 at 20°C did not show any increase in larval mortalities of the mixtures for exposure periods between 24–96 hours. The larval mortalities obtained for an atmosphere contained 20 and 50% CO2 alone at 20 and 30°C was (0–6%) and (10–40%), respectively, after 10 days exposure period.  相似文献   

20.
A Bowman-Birk inhibitor with activity against gut proteases of Helicoverpa armigera was extracted in 0.1 M sodium phosphate buffer from defatted seed flour of Albizia lebbeck. It was purified to 29.62 folds with 51.43% recovery using ammonium sulfate precipitation, gel filtration chromatography on Sephadex G-100 column and ion exchange chromatography on DEAE-Sephadex A50. The purified protein had a molecular weight of 12,303 daltons as determined by SDS-PAGE. It was found to be heat stable up to 60°C and had two pH optima of 7.5 and 9.0. The inhibitor exhibited non-competitive pattern of inhibition with a low Ki value of 0.2 μM. The inhibitor was found to be susceptible to varying concentrations of reducing agents like DTT and 2-mercaptoethanol, thereby indicating the role of disulphide bridges in maintaining its three dimensional structure and stability. The purified inhibitor caused mortality and suppressed larval growth of Pieris brassicae larvae. It was also found to be effective against gut trypsin extracted from Spodoptera littoralis. The sequence of the genes encoding for such inhibitors can be determined and the genes expressing protease inhibitors can be used in vegetable crops to confer resistance against insect pests and other plant pathogens.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号